David Cameron, John Humphrys clash over AV

The BBC has admitted that Today presenter John Humphrys could have been "clearer" about how the alternative vote (AV) system works in a fraught interview with David Cameron.

In a discussion this morning on the Radio 4 programme, Cameron accused Humphrys of giving listeners incorrect information about the way the AV system works. He also said that the presenter should go "back to school".

The interview was staged ahead of the referendum on Thursday in which voters will decide whether to ditch the old first-past-the-post system in favour of AV, which involves voters ranking parliamentary candidates in order of preference.

Under AV, candidates receiving the fewest votes in each round will be eliminated and their second preferences distributed among the remaining candidates. The process continues until someone has a 50% backing to get elected, or there are no more votes to distribute.

Humphrys and Cameron clashed after the presenter told the prime minister that it was incorrect to argue that some votes could be counted more than others under AV.

Cameron responded: "It is quite worrying if actually the lead broadcaster on the BBC doesn't understand the system. You don't understand the system you are supposed to be explaining to the public. I do think that's worrying. Back to school."

In a statement, the BBC said that Today and other BBC programmes had already "spelled out in great detail how AV would work" if the system was introduced.

However, a spokesman for the corporation admitted that Humphreys had not been clear enough in his explanation of the specific technicalities.

"During a lively Today interview, David Cameron and John Humphrys disagreed over a technicality when the AV referendum was discussed," he said.

"John Humphrys was trying to reflect the point of contention between the campaigns over whether some people, in effect, have more than one vote under AV. In hindsight, he could have made this clearer."